Substrate carrier with array of independently controllable heater elements

ABSTRACT

A substrate carrier is described with an array of independently controllable heater elements. In one example an apparatus includes a substrate carrier to carry a substrate for processing, a plurality of resistive heating elements in the carrier to heat the substrate by heating the carrier, a power supply to supply power to the heating elements, a power controller to provide a control signal, the control signal to control an amount of current applied to each of the heating elements, and a plurality of power interfaces in the carrier each coupled to a heating element to receive the power from the power supply and the control signal from the controller and to modulate the power applied to a respective coupled heating element in response to the control signal.

FIELD

The present description relates to the field of semiconductor andmicromechanical substrate processing using a substrate carrier in achamber and, in particular, independently controlling heating todifferent areas of the substrate using heating elements.

BACKGROUND

Semiconductor and micromechanical systems are formed on substrates, suchas silicon wafers. A complex sequence of operations involvingdepositing, etching, shaping, patterning and washing are applied to thesubstrate to form the tiny structures that form the semiconductor andmicromechanical parts on the substrate. These structures are madesmaller and closer together in order to reduce cost. The smallerstructures require less material, less power to operate, and less spaceto house. The smaller structures are also often faster than largerstructures and may have many more advantages.

In order to make smaller structures, the fabrication processes must bemore precise. Every aspect of the process is improved over time toenable smaller structures. Many of the fabrication processes, such aselectron beam deposition, plasma deposition, plasma-enhanced chemicalvapor deposition (PECVD), resist stripping, and plasma etching, etc. areaffected by the temperature of the silicon wafer. If the temperature ofthe wafer in one location is different from that in another location,then the result of the process will be different in the differentlocations. In addition, if the temperature is different from thetemperature for which the process was designed, then the results of theprocess will not be what was designed. As a result, temperaturevariations during fabrication may cause some structures to work poorlyor even be inoperable.

The temperature of a substrate in a processing chamber can be measuredusing an infrared camera or a heat sensor on the substrate. In somecases a special wafer is used that has one or more thermal sensors andthat store temperatures in a memory during a test process. A process isperformed with the special wafer in the chamber and then the process isadjusted based on the measured temperatures.

SUMMARY

A substrate carrier is described with an array of independentlycontrollable heater elements. In one example an apparatus includes asubstrate carrier to carry a substrate for processing, a plurality ofresistive heating elements in the carrier to heat the substrate byheating the carrier, a power supply to supply power to the heatingelements, a power controller to provide a control signal, the controlsignal to control an amount of current applied to each of the heatingelements, and a plurality of power interfaces in the carrier eachcoupled to a heating element to receive the power from the power supplyand the control signal from the controller and to modulate the powerapplied to a respective coupled heating element in response to thecontrol signal.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention are illustrated by way of example,and not limitation, in the figures of the accompanying drawings inwhich:

FIG. 1 is a process flow diagram of a subtractive approach todetermining a temperature profile of a substrate attached to a substratecarrier according to an embodiment.

FIG. 2 is a process flow diagram of an additive approach to determininga temperature profile of a substrate attached to a substrate carrieraccording to an embodiment.

FIG. 3 is a process flow diagram of an additive and subtractive approachto determining a temperature profile of a substrate attached to asubstrate carrier according to an embodiment.

FIG. 4 is a process flow diagram of a passive carrier approach todetermining a temperature profile of a substrate attached to a substratecarrier according to an embodiment.

FIG. 5 is a graph of resistance over temperature of an electricalresponse characteristic of a thermal device and a heating elementaccording to an embodiment.

FIG. 6 is a graph of current over time of power from a carrier powersupply according to an embodiment.

FIG. 7 is a diagram of a control box coupled to a heated substratecarrier according to an embodiment.

FIG. 8 is an isometric view of an electrostatic chuck in accordance withan embodiment of the invention.

FIG. 9 is a schematic of a plasma etch system including a chuck assemblyin accordance with an embodiment of the present invention.

DETAILED DESCRIPTION

As described herein an array of heating elements in a support, carrier,pedestal, or chuck that carries a substrate in a processing chamber maybe used to measure the temperature of the substrate support. The heatingelements have a resistance that is related to temperature so that theresistance of a heating element can be measured as an indication of thetemperature of the support. This provides an indication of thetemperature of the substrate immediately above the support. The array ofheater elements provides independent temperature measurements atdifferent positions on the support. The different measurements allowtemperature variations across the substrate to be measured. This allowsfor the heaters to be operated to even out the temperature or for thesupport to be modified to correct for the inconsistent temperatures.

In some cases, an electrostatic chuck (ESC) is fitted with an array ofheater elements to allow for the temperature of the ESC to be adjusteddifferently at different positions across the surface of the ESC. Whilethe present description is presented in the context of an ESC, thestructures and techniques may also be applied to other types ofsubstrate carriers. The array of heater elements may also be used astemperature sensors or thermal sensors. This allows for the temperatureof the substrate to be determined. The corresponding heater element maythen be activated or deactivated to accommodate the measuredtemperature.

The heater elements are wired to receive an electrical current and theheating elements by nature typically have a linear relationship ofresistance to temperature. The heater elements that are often used in anESC have a metallization material formulated of tungsten and alumina.This metalized material like many others responds to temperature with alinear relationship that can be used for measurement and control.

By using the heater elements, external temperature sensors are avoided,simplifying the ESC and the processing chamber. There may also be moreaccurate information on temperature variations across the substrate bymeasuring the temperature at many closely arrayed points.

The thermal sensor data from the heater elements can be used to feedopen loop models or a time based closed loop control PID(Proportional-Integral-Derivative) scheme. The measurements may be takeninside and outside the RF (Radio Frequency) hot environment and may beimplemented in many different ways in plasma etch and other processes.The thermal sensor may be used for open loop verification of the ESC andsubstrate temperature, for closed loop control of the ESC and substratetemperature, and for diagnostics of damaged heating arrays or coolingchannel elements.

An alternative to the described approach is to place a thermal sensornear each heater element. In such a case, each heater element requires apair of wires to control the rate at which it applies heat to the ESC.Each thermal sensor also requires a pair of wires to send temperaturereadings. The footprint for this system is larger to accommodate thewiring, the switching, the power distribution, and the control circuitryof the thermal probes or RTDs (Resistance Temperature Detector)

The larger footprint takes space which could be used for switchingelements or other logic devices in the ESC. There would also be space ina control box to receive all the additional wires and track and maintainall of the temperature measurements. In addition to the space required,complicated I/O and mechanical interfaces to external processing devicesare required. This additional cost and complexity might lead to designsthat are constrained to fewer less accurate measurements in order toreduce cost.

The described techniques may be applied to wafers, pedestals, carriers,and electrostatic chucks with multiple heater zones. These may alsoinclude bulk heating zones. In some embodiments there are more than 150mini resistive heaters that are used in the RF hot environment, butthere may be 300 or more. This may all be accommodated with a 300 mmsilicon wafer carrier. As described below, the control architecture maybe scaled to support the hundreds of heating zones. This architectureprovides real time control to devices both internally and externally ofthe RF hot environment, but does not require extra temperaturemeasurement hardware.

To measure the temperature, the heating current to a particular heaterelement is turned off. A measurement current is then driven through theheater element. Sensor hardware may be used to measure the full currentor a partial current going through the heater element. In someembodiments a PWM (Pulse Width Modulation) frequency may be used.

The relationship between the measured current and the temperature of theESC can be accurately measured in several different ways. One way is bytiming the activated array element and measuring the current and thevoltage used by the element. Current or voltage or both may be measuredby devices such as inline shunt resistors, current clamps, Hall Effectsensors, and voltage dividers. The signal can be digitized by analog todigital converters for later processing.

FIG. 1 is a process flow diagram of a subtractive approach todetermining a temperature profile of a substrate attached to anelectrostatic chuck or any other substrate carrier featuring heaters asdescribed herein. At 2 a first combined current load is measured. Thiscurrent load is the current consumed by all of the heating elements ofthe carrier or of a group of heating elements that are all powered witha single current supply. In this process, single heating elements orsmall groups of heating elements may be individually turned on or off.

At 4 the power is disconnected from one of the heating elements of thecarrier. In this example, the heating elements have a common powersupply but may individually be controlled or controlled in groups. Eachheating element or group of heating elements may be switched off,de-powered, or disconnected in some other way so that the selectedheating element is no longer consuming power and is no longer heatingthe carrier or the substrate that is being carried. This is referred toas element i, where i is a variable that is incremented through all ofthe heating elements that will be measured.

With the selected heating element disconnected the current load ismeasured again at 6. This provides a second combined current load forall heating elements after disconnecting power to the first selectedheating element. At 8 the difference between the first and the secondcombined current loads is determined. This provides the current that wasbeing consumed by the selected heating element or element i. At 10 thetemperature of the selected heating element is determined.

The temperature of the heating element is directly related to itsresistance. The resistance may be determined using the current and knownvoltage. If the voltage is not known then this may also be measured atthe same time as the current load. The resistance has a linearrelationship to the temperature of the heating element which is the sameas the temperature of the carrier in the area of the heating element.The temperature of the heating element may then be related to thesubstrate that is being carried by using a model or a look up tablebased on empirical measurements. With the temperature at the heatingelement determined, the system may then move to reconnect power to theselected heating element at 12.

At 14 another heating element is selected. If the first element isdesignated as element 1, wherein i=1, then i is incremented and the nextelement is element 2, wherein i=2. After incrementing i or after simplyselecting the next heating element, the process returns to 2 and theoperations of disconnecting, measuring a current load, determining adifference, and temperature and reconnecting the heater element arerepeated for each of the other heating elements of the to determine atemperature at each of the heating elements of the carrier.

After all of the heating element are measured then the process ends. Inthis process, the selection of heating elements may be ordered with anoffset or spacing. Since a heating element is temporarily turned off tomake the temperature measurement, the carrier will be slightly cooler inthe area of that heating element. The next heating element to bemeasured may be spaced some distance from the last heating element sothat the local cooling does not affect the next measurement. The carrierwill have time to recover before another heating element in the samearea is measured.

As mentioned above inside of measuring the temperature at each heatingelement, the heating elements may be grouped. In this case, thetemperature will be averaged over the group of heating elements. As anexample, the determined current, voltage, or resistance may be dividedor distributed among the heating elements of the measured subset. Thismay be done simply by dividing by the number of heating elements or inanother way. The temperature may then be determined using the dividedresistance.

FIG. 2 is a process flow diagram of an additive approach to determininga temperature profile of a substrate attached to an electrostatic chuckor other substrate carrier with heaters. At 22 a first one of theheating elements is switched off, de-powered, or disconnected from usingpower in some way. At 24 a first combined current load is measured. Thiscurrent load is the current consumed by all of the heating elements ofthe carrier or of a group of heating elements that are all powered witha single current supply excluding the heating element for which thetemperature is to be measured. In this process, a single heating elementor small group of heating elements turned off. Power is supplied to theother heating elements and this is what is measured. At 26 power isrestored to the selected heating element i, and at 28 the current ismeasured again. As in the example of FIG. 1, the voltage may also bemeasured with the current or the voltage may be maintained at a constantdepending on the particular power supply implementation.

At 30 the difference between the two measurements is determined. Thisisolates the power consumed by the selected heating element, i. At 32this difference is used to determine a temperature of the heatingelement. The temperature is directly related to the resistance which maybe determined using the current and the voltage difference. Thistemperature determination may then be stored in a log with a measurementtime for use in modifying the process, detecting production variations,improving yield and other purposes.

At 34 the process ends if all of the heating elements have been measuredor it returns to the beginning to go to the next heating element. Thismay be performed by incrementing i to represent the next heating elementand then repeating the operations of disconnecting power, measuring thecurrent, connecting the power, measuring the current again, determininga difference, and determining a temperature for each of the otherheating elements.

FIG. 3 is a process flow diagram of an alternative additive andsubtractive approach to determining a temperature profile of a substrateattached to an electrostatic chuck or any other substrate carrierfeaturing heaters as described herein. As above, this process isparticularly well suited to use during a plasma process but may also beused in other circumstances. At 40 the voltage supplied to all of theresistive heating elements is measured. The measurement may be made at acentral power supply that supplies all of the resistive heating elementstogether. If the heating elements are powered in smaller groups, e.g.four separate power supplies are each used for a separate one fourth ofthe heating elements, then this process may be applied separately toeach group. This operation may also be applied to the first twoprocesses described above.

At 42 a first combined current load is measured. This current load isthe current consumed by all of the heating elements of the carrier or ofa group of heating elements that are all powered with a single currentsupply. In this process, single heating elements or small groups ofheating elements may be individually turned on or off. This process isperformed while the heating elements are in normal operation.Accordingly, most of the heating elements will be in an intermediatepower state as neither fully on nor fully off. In other words thecurrent duty cycle will be at some intermediate value.

For the next operation a particular single one of the heating elementsis selected as the start of the process. This element is designated e.g.as element 1 or element 0 and a variable i=0 to track the processthrough each element. At 44 the power is increased from the firstheating element i=0. In some embodiments, the heating element goes tofull ON or a 100% duty cycle. This ON states is required only longenough to measure the current. At 46, the current load of all of theheating elements is measured again after increasing the power. At 48 thepower to the single heating element is then switched to OFF. The otherheating elements of the carrier are not affected.

With the selected heating element disconnected at 48 the current load ismeasured again at 50. This provides a third combined current load forall heating elements after disconnecting power to the first selectedheating element. The carrier may then be returned to normal operationand the temperature of the carrier may be stabilized at 52.

At 56 the differences between the first, second and third combinedcurrent loads are determined. This provides the current that was beingconsumed by the selected heating element or element i. At 56 thetemperature of the selected heating element is determined using thesedifferences.

At 58 another heating element is selected. If the first element isdesignated as element 1, wherein i=1, then i is incremented and the nextelement is element 2, wherein i=2. After incrementing i or after simplyselecting the next heating element, the process returns to 40 or to 42if the voltage is fixed and the operations are repeated at each of theheating elements of the carrier. After all of the heating element aremeasured then the process ends.

FIG. 4 is a process flow diagram of an alternative approach todetermining a temperature profile of a substrate attached to a passiveelectrostatic chuck or any other substrate carrier featuring heaters asdescribed herein. This process is particularly well suited to use as atest wafer during a plasma process but may also be used in othercircumstances. To instrument processes in a particular chamber, a testwafer is often used. The test wafer has a top surface with a hundred ormore thermal sensors coupled to memory cells. The test wafer is attacheda carrier while a process is being run and the test wafer logstemperature at each thermal sensor during the process. After theprocess, the test wafer is removed and the temperature logs are read.The process may then be adjusted based on the temperature data.

The process of FIG. 4 collects similar data using a heated carrier witha passive wafer on top. The heaters are used to collect the temperaturedata without the need for a test wafer. The temperature of the wafer maybe estimated based on the temperature of the carrier immediately belowthe carrier. For such a test, the heating elements are not used forheating bur only for measuring temperature. In contrast to the testwafer, the process of FIG. 4 allows temperature data to be collected inreal time or during the process rather than waiting until the end of theprocess. This allows the test process to be modified during the test toobtain the desired results more quickly.

At 60 the voltage supplied to all of the resistive heating elements ismeasured. This is normally the primary power supply voltage that issupplied to all of the resistive heating elements. The current at 62will be zero or negligible because the carrier is not being used to addheat to the test process. At 64 a particular single one i of the heatingelements is selected as the start of the process and power is applied.This will be a known power selected to provide the best temperaturemeasurement. As explained below a higher current will typically providea higher response to temperature. With the one powered heating element,the current load is measured at 66. This current is almost completelydue to the selected heating element. The selected heating element maythen be returned to OFF, the normal state for this cycle.

At 68 the difference between the first and second combined current loadsis determined. This subtracts out noise, current leakage and otherfactors that move the OFF state current away from zero. At 70 thetemperature of the selected heating element is determined using thesedifferences.

At 72 another heating element is selected and the process is repeateduntil all of the heating elements are measured. That is the end of thismeasurement cycle. As with FIGS. 1-3, the process may be completedthrough all of the heating elements for as long as desired. Thisprovides a continuous temperature map over time.

FIG. 5 is a graph of an electrical response characteristic of a typicalcommercial resistive thermal device and of a typical commercial heatingelement for comparison. The vertical scale shows the resistance of thecomponent and the horizontal scale shows the temperature of thecomponent. The upper line corresponds to a resistive thermal devicedesigned specifically for measuring temperature by changing resistance.As shown at room temperature of about 20° C., the resistance is about108Ω. This increases to almost 140 Ω at 100° C. As shown, the responseof the thermal device within the illustrated temperature range isapproximately linear. This allows temperatures to be easily and quicklydetermined based on the measured resistance.

The response of a heating element is shown on the lower line. This lineis also approximately linear but with a lower slope. As a result thetemperature measurement is less accurate. This is a result of thethermal device being specifically designed to exhibit a large change inresponse to temperature. The heating element is designed to efficientlyconvert current to heat. With modifications, the response of the heatingelement may be improved. In this example, at room temperature theheating element has a resistance of about 70Ω. At 100° C., theresistance has increased to about 90Ω. While the thermal device shows achange of about 30 Ω between the two temperatures, the heating elementshows a change of only about 20 Ω through the same temperature.

FIG. 6 is a graph of current over time from a substrate carrier powersupply as heating elements are turned on and off. This shows how theadditive and subtractive techniques described above may be used. Thegraph shows different current levels from a common main power supply asthe state of various heating elements is changed. The first state 230corresponds to an average current or power when most of the heatingelements are powered. At 232 one or more heating elements are switchedfrom ON to OFF. This results in a reduction in the total current. At 234the low current stage is ended and at 236 the heating elements arereturned to an ON state. The difference between the current at 234 andat 236 may be used to determine the current consumed by the heatingelements that were turned from ON to OFF. This may then be used todetermine the temperature in the vicinity of those heating elements.

In a similar way the current at 238 reflects an average or normal powerand at 240 a second set of one or more heating elements are switchedfrom an OFF to an ON state. This increases the total current. At 242 theON cycle ends and at 244 the heating elements are returned to an OFFstate. The difference between the current at 242 and 244 may be used todetermine the current draw and with it the temperature in the vicinityof the second set of heating elements. The shape of curve is shown asrectangular in order to simplify the drawing figure. In a real systemthere will be settling time after each change as the heating elementsand the power supply adjust to the change in state. The response of theheating elements and of the power supply will not be immediate anddirect as shown.

FIG. 7 is a block diagram of a substrate carrier and a temperaturecontrol system suitable for use with the method described above. Thesystem has a control box 502 that is coupled to a terminal 504. Theterminal may be in the form of a conventional computer that runs processcontrol or temperature control software with a user interface to allowan operator to control the machine processes. The terminal may have aprocessor coupled to a mass storage medium, a user interface and aninterface to the control box. The terminal may have other componentssuch as high speed memory, wireless or wired communications interfaces,additional processors, etc. The mass storage may be in the form of amachine-readable medium having instructions, parameters, and variouslogs, in solid state, optical, or magnetic storage. The control boxcontrols the operation of the substrate carrier 506 in response toinstructions or commands from the terminal. The control box may be ableto operate autonomously subject to general commands from the terminal.The control box may control other functions of the carrier such as clampelectrodes, coolants, gas injection, and other functions not shown herein order not to obscure the features of temperature measurement shownhere.

The control box includes a heating element power controller 510 and apower supply 512. The power supply provides a single power feed 516 on asingle line to a fan-out distributor 518 within the substrate carrier506. The fan-out distributor supplies the power from the power supply512 to all of the heating elements 530 of the carrier 506. This powermay be significant depending on the implementation. In the illustratedembodiment there are 150 heating elements each capable of drawing 10watts, so the power supply provides 1500 watts to the carrier. Thevoltage, current, and other parameters are measured and controlled bythe power supply 512 in the control box.

The power controller of the control box sends control signals through adata interface 514 to a carrier controller 522 of the carrier 506. Thecontrol signals may be used to adjust the power supplied to each of theheating elements 530, change from an ON state to an OFF state and toadjust other parameters of the carrier. In this example, the datasignals set the parameters of operation of each of the heaters based oninformation from the terminal or generated within the control box powercontroller. The control signal 514 may be a sequence of packets whereeach packet sets parameters for a different one of the heating elements.Packet headers or identification fields might be used to identify aparticular one of the heating elements so that the status of aparticular heating element may be changed with any packet and before itmight have a turn in an ordered sequence of packets.

In this example, the carrier controller receives the status updatepackets for each heating element and generates a different PWM (PulseWidth Modulated) analog signal to each of the heating elements. To set aparticular heater to an OFF state, the PWM signal is a zero duty cyclesignal or a low signal. To set different amounts of heating, thecontroller adjusts the duty cycle of the respective PWM signal for eachheating element. This allows each heating element to be independentlycontrolled using a unique signal to that element. In this example thereare 150 unique individual PWM connections, one for each heating element.The PWM signals are generated by the carrier controller and received ata power interface for each heating element. The unique signals from thecarrier controller may be very simple so that they are only an on/offcycle of an optical signal indicating the duty cycle of the PWM pulses.These may be converted directly into a gate driver of an amplifier tothe respective heating element.

At each respective heating element 530, there is a power interface 528and the actual resistive heating element 530. The power interfacereceives the PWM signal at an isolator 532 such as an opto-isolator andapplies the PWM signal to an amplifier. The amplifier receives power 520from the fan-out distributor and modulates the received power based onthe PWM signal. The modulated power is applied to the resistive heater530 to heat the carrier and therefore to heat the substrate. The opticalsignal is used within the carrier to shield the sensitive signal fromnoise within the carrier. The plasma, bias power, active ions and otheraspects of a plasma chamber may interfere with an electrical signal andespecially an analog electrical signal.

Using this system, the terminal 504 may be used to initiate atemperature measurement cycle. Alternatively, the control box 510 mayoperate a temperature measurement cycle. The control box will sendcontrol signals 514 to the carrier controller 522 to set the duty cyclesof particular ones of the heating elements to zero and then back againto normal in a particular order and with a particular timing asdescribed in FIGS. 1-4. The power supply will monitor the changes incurrent draw from the heaters as each heater is turned on and offthroughout the carrier. This temperature information may be used toincrease or decrease the duty cycle applied to each heater or to providemetrics on a particular process. Each heating element may be switchedfrom ON or OFF in microseconds and a change in heating requires a fewseconds to cause a new stable temperature at the carrier. For a processthat takes a few minutes, the temperature may be measured many timesthrough the process.

Using 150 heaters provides very specific information about a small areaof the carrier. More or fewer heaters may be used, depending on thedesired precision. In addition, since each heating element isindividually controlled, the controller may test the temperature only atsome of the heaters. Instead of 150 different temperature locations, thecontroller may use only 50 different locations by measuring thetemperature at only 50 of the available heaters. While 150 heatingelements are suggested, there may be more or fewer depending on thedesired precision. There may also be other heaters such as a few largerhigh power heaters to provide more heating with a coarse level ofcontrol. The coarse level of control may then be adjusted using the manysmaller heaters. While in this example each heater is controlledindividually, several heaters may be connected to a single PWM input andamplifier 528 so that a group of heaters are controlled as a group.

FIG. 8 is an isometric view of an assembled electrostatic chuck. Asupport shaft 212 supports a base plate 210 through an isolator 216. Amiddle isolator plate 208 and an upper cooling plate 206 are carried bythe base plate. The top cooling plate 206 carries a dielectric puck 205on the top surface of the heater plate. The puck has an upper circularplatform to support a workpiece 204 and a lower concentric circular base207 to attach to the heater plate. The upper platform has internalelectrodes to electrostatically attach the workpiece. The workpiece mayalternately be clamped, vacuumed or attached in another way.

There is an adhesive bond 218 between the puck 215 and the top coolingplate 206 to hold the ceramic of the top plate to the metal of thecooling plate. Heaters may be formed in the top plate or the middleheater plate. In such an embodiment, the middle plate performs otherfunctions but is no longer the location of the heaters. The carriercontroller may be attached to the cooling plate or to any otherlocation. The resistive heating elements and associated power interfacemay be embedded into the ceramic of the puck. This places the heaters asclose as possible to the substrate on the top plate for the greatesteffect.

The ESC is able to control the temperature of the workpiece usingresistive heaters in the puck as described above. In addition, coolantfluid may be used in the cooling plate. Electrical power, controlsignals, coolant, gases, etc. are supplied to the coolant plate 206 andthe puck 205 through the support shaft 212. The ESC may also bemanipulated and held in place using the support shaft.

FIG. 9 is a partial cross sectional view of a plasma system 100 having apedestal 128 according to embodiments described herein. The pedestal 128has an active cooling system which allows for active control of thetemperature of a substrate positioned on the pedestal over a widetemperature range while the substrate is subjected to numerous processand chamber conditions. The plasma system 100 includes a processingchamber body 102 having sidewalls 112 and a bottom wall 116 defining aprocessing region 120.

A pedestal, carrier, chuck or ESC 128 is disposed in the processingregion 120 through a passage 122 formed in the bottom wall 116 in thesystem 100. The pedestal 128 is adapted to support a substrate (notshown) on its upper surface. The substrate may be any of a variety ofdifferent workpieces for the processing applied by the chamber 100 madeof any of a variety of different materials. The pedestal 128 mayoptionally include heating elements (not shown), for example resistiveelements, to heat and control the substrate temperature at a desiredprocess temperature. Alternatively, the pedestal 128 may be heated by aremote heating element, such as a lamp assembly.

The pedestal 128 is coupled by a shaft 126 to a power outlet or powerbox 103, which may include a drive system that controls the elevationand movement of the pedestal 128 within the processing region 120. Theshaft 126 also contains electrical power interfaces to provideelectrical power to the pedestal 128. The power box 103 also includesinterfaces for electrical power and temperature indicators, such as athermocouple interface. The shaft 126 also includes a base assembly 129adapted to detachably couple to the power box 103. A circumferentialring 135 is shown above the power box 103. In one embodiment, thecircumferential ring 135 is a shoulder adapted as a mechanical stop orland configured to provide a mechanical interface between the baseassembly 129 and the upper surface of the power box 103.

A rod 130 is disposed through a passage 124 formed in the bottom wall116 and is used to activate substrate lift pins 161 disposed through thepedestal 128. The substrate lift pins 161 lift the workpiece off thepedestal top surface to allow the workpiece to be removed and taken inand out of the chamber, typically using a robot (not shown) through asubstrate transfer port 160.

A chamber lid 104 is coupled to a top portion of the chamber body 102.The lid 104 accommodates one or more gas distribution systems 108coupled thereto. The gas distribution system 108 includes a gas inletpassage 140 which delivers reactant and cleaning gases through ashowerhead assembly 142 into the processing region 120B. The showerheadassembly 142 includes an annular base plate 148 having a blocker plate144 disposed intermediate to a faceplate 146.

A radio frequency (RF) source 165 is coupled to the showerhead assembly142. The RF source 165 powers the showerhead assembly 142 to facilitategeneration of plasma between the faceplate 146 of the showerheadassembly 142 and the heated pedestal 128. In one embodiment, the RFsource 165 may be a high frequency radio frequency (HFRF) power source,such as a 13.56 MHz RF generator. In another embodiment, RF source 165may include a HFRF power source and a low frequency radio frequency(LFRF) power source, such as a 300 kHz RF generator. Alternatively, theRF source may be coupled to other portions of the processing chamberbody 102, such as the pedestal 128, to facilitate plasma generation. Adielectric isolator 158 is disposed between the lid 104 and showerheadassembly 142 to prevent conducting RF power to the lid 104. A shadowring 106 may be disposed on the periphery of the pedestal 128 thatengages the substrate at a desired elevation of the pedestal 128.

Optionally, a cooling channel 147 is formed in the annular base plate148 of the gas distribution system 108 to cool the annular base plate148 during operation. A heat transfer fluid, such as water, ethyleneglycol, a gas, or the like, may be circulated through the coolingchannel 147 such that the base plate 148 is maintained at a predefinedtemperature.

A chamber liner assembly 127 is disposed within the processing region120 in very close proximity to the sidewalls 101, 112 of the chamberbody 102 to prevent exposure of the sidewalls 101, 112 to the processingenvironment within the processing region 120. The liner assembly 127includes a circumferential pumping cavity 125 that is coupled to apumping system 164 configured to exhaust gases and byproducts from theprocessing region 120 and control the pressure within the processingregion 120. A plurality of exhaust ports 131 may be formed on thechamber liner assembly 127. The exhaust ports 131 are configured toallow the flow of gases from the processing region 120 to thecircumferential pumping cavity 125 in a manner that promotes processingwithin the system 100.

A system controller 170 is coupled to a variety of different systems tocontrol a fabrication process in the chamber. The controller 170 mayinclude a temperature controller 175 to execute temperature controlalgorithms (e.g., temperature feedback control) and may be eithersoftware or hardware or a combination of both software and hardware. Thesystem controller 170 also includes a central processing unit 172,memory 173 and input/output interface 174. The temperature controllerreceives a temperature reading 143 from a sensor (not shown) on thepedestal. The temperature sensor may be proximate a coolant channel,proximate the wafer, or placed in the dielectric material of thepedestal. The temperature controller 175 uses the sensed temperature ortemperatures to output control signals affecting the rate of heattransfer between the pedestal assembly 142 and a heat source and/or heatsink external to the plasma chamber 105, such as a heat exchanger 177.

The system may also include a controlled heat transfer fluid loop 141with flow controlled based on the temperature feedback loop. In theexample embodiment, the temperature controller 175 is coupled to a heatexchanger (HTX)/chiller 177. Heat transfer fluid flows through a valve(not shown) at a rate controlled by the valve through the heat transferfluid loop 141. The valve may be incorporate into the heat exchanger orinto a pump inside or outside of the heat exchanger to control the flowrate of the thermal fluid. The heat transfer fluid flows throughconduits in the pedestal assembly 142 and then returns to the HTX 177.The temperature of the heat transfer fluid is increased or decreased bythe HTX and then the fluid is returned through the loop back to thepedestal assembly.

The HTX includes a heater 186 to heat the heat transfer fluid andthereby heat the substrate. The heater may be formed using resistivecoils around a pipe within the heat exchanger or with a heat exchangerin which a heated fluid conducts heat through an exchanger to a conduitcontaining the thermal fluid. The HTX also includes a cooler 188 whichdraws heat from the thermal fluid. This may be done using a radiator todump heat into the ambient air or into a coolant fluid or in any of avariety of other ways. The heater and the cooler may be combined so thata temperature controlled fluid is first heated or cooled and then theheat of the control fluid is exchanged with that of the thermal fluid inthe heat transfer fluid loop.

The valve (or other flow control devices) between the HTX 177 and fluidconduits in the pedestal assembly 142 may be controlled by thetemperature controller 175 to control a rate of flow of the heattransfer fluid to the fluid loop. The temperature controller 175, thetemperature sensor, and the valve may be combined in order to simplifyconstruction and operation. In embodiments, the heat exchanger sensesthe temperature of the heat transfer fluid after it returns from thefluid conduit and either heats or cools the heat transfer fluid based onthe temperature of the fluid and the desired temperature for theoperational state of the chamber 102.

Electric heaters (not shown) are used in the ESC to apply heat to theworkpiece assembly. The electric heaters in the form of resistiveelements are coupled to a power supply 179 that is controlled by thetemperature control system 175 to energize the heater elements to obtaina desired temperature.

The heat transfer fluid may be a liquid, such as, but not limited todeionized water/ethylene glycol, a fluorinated coolant such asFluorinert® from 3M or Galden® from Solvay Solexis, Inc. or any othersuitable dielectric fluid such as those containing perfluorinated inertpolyethers. While the present description describes the pedestal in thecontext of a PECVD processing chamber, the pedestal described herein maybe used in a variety of different chambers and for a variety ofdifferent processes.

A backside gas source 178 such as a pressurized gas supply or a pump andgas reservoir are coupled to the chuck assembly 142 through a mass flowmeter 185 or other type of valve. The backside gas may be helium, argon,or any gas that provides heat convection between the wafer and the puckwithout affecting the processes of the chamber. The gas source pumps gasthrough a gas outlet of the pedestal assembly described in more detailbelow to the back side of the wafer under the control of the systemcontroller 170 to which the system is connected.

The processing system 100 may also include other systems, notspecifically shown in FIG. 4, such as plasma sources, vacuum pumpsystems, access doors, micromachining, laser systems, and automatedhandling systems, inter alia. The illustrated chamber is provided as anexample and any of a variety of other chambers may be used with thepresent invention, depending on the nature of the workpiece and desiredprocesses. The described pedestal and thermal fluid control system maybe adapted for use with different physical chambers and processes.

As used in the description of the invention and the appended claims, thesingular forms “a”, “an” and “the” are intended to include the pluralforms as well, unless the context clearly indicates otherwise. It willalso be understood that the term “and/or” as used herein refers to andencompasses any and all possible combinations of one or more of theassociated listed items.

The terms “coupled” and “connected,” along with their derivatives, maybe used herein to describe functional or structural relationshipsbetween components. It should be understood that these terms are notintended as synonyms for each other. Rather, in particular embodiments,“connected” may be used to indicate that two or more elements are indirect physical, optical, or electrical contact with each other.“Coupled” my be used to indicate that two or more elements are in eitherdirect or indirect (with other intervening elements between them)physical, optical, or electrical contact with each other, and/or thatthe two or more elements co-operate or interact with each other (e.g.,as in a cause an effect relationship).

The terms “over,” “under,” “between,” and “on” as used herein refer to arelative position of one component or material layer with respect toother components or layers where such physical relationships arenoteworthy. For example in the context of material layers, one layerdisposed over or under another layer may be directly in contact with theother layer or may have one or more intervening layers. Moreover, onelayer disposed between two layers may be directly in contact with thetwo layers or may have one or more intervening layers. In contrast, afirst layer “on” a second layer is in direct contact with that secondlayer. Similar distinctions are to be made in the context of componentassemblies.

It is to be understood that the above description is intended to beillustrative, and not restrictive. For example, while flow diagrams inthe figures show a particular order of operations performed by certainembodiments of the invention, it should be understood that such order isnot required (e.g., alternative embodiments may perform the operationsin a different order, combine certain operations, overlap certainoperations, etc.). Furthermore, many other embodiments will be apparentto those of skill in the art upon reading and understanding the abovedescription. Although the present invention has been described withreference to specific exemplary embodiments, it will be recognized thatthe invention is not limited to the embodiments described, but can bepracticed with modification and alteration within the spirit and scopeof the appended claims. The scope of the invention should, therefore, bedetermined with reference to the appended claims, along with the fullscope of equivalents to which such claims are entitled.

What is claimed is:
 1. An apparatus comprising: a substrate carrier to carry a substrate for processing; a plurality of resistive heating elements in the carrier to heat the substrate by heating the carrier; a power supply to supply power to the heating elements; a power controller to provide a control signal, the control signal to control an amount of current applied to each of the heating elements; and a plurality of power interfaces in the carrier each coupled to a heating element to receive the power from the power supply and the control signal from the controller and to modulate the power applied to a respective coupled heating element in response to the control signal.
 2. The apparatus of claim 1, wherein the power controller commands an ON state and an OFF state for each heating element by controlling power supplied to each heating element.
 3. The apparatus of claim 2, wherein the power supply measures a power supplied to the heating elements when the power controller controls an ON and an OFF state of a heating element to determine a power of the respective heating element.
 4. The apparatus of claim 1, further comprising a carrier controller in the carrier coupled to each of the plurality of power interfaces, wherein the power controller provides a digital control signal to the carrier controller and wherein the carrier controller controls the power modulation of the power interface.
 5. The apparatus of claim 4, wherein the carrier controller generates a pulse width modulated signal to each power interface and wherein each power interface modulates the received power from the power supply using the received pulse width modulated signal.
 6. The apparatus of claim 5, wherein the pulse width modulated signal is an optically modulated signal sent through an optical connection of the carrier and wherein each power interface comprises an opto-isolator coupled to the received pulse width modulated signal and an amplifier and wherein the opto-isolator provides the received pulse width modulated signal to the amplifier to control the amplifier.
 7. The apparatus of claim 1, further comprising a fan-out distributor in the carrier to receive the power from the power supply and to distribute the received power to each power interface.
 8. The apparatus of claim 7, wherein the power supply is coupled using a single power line to the fan-out distributor in the carrier.
 9. The apparatus of claim 1, wherein the power supply measures the voltage and current supplied to the heating elements.
 10. The apparatus of claim 1, wherein the carrier is ceramic and the resistive heating elements and the power interfaces are embedded in the ceramic.
 11. A method comprising: supplying power to a plurality of heating elements from a common power supply, the heating elements being in a substrate carrier to heat the substrate by heating the carrier, the carrier to carry the substrate during processing; generating a control signal from a power controller to control an amount of current applied to each of the heating elements; receiving the power from the power supply at each of a plurality of power interfaces in the carrier each coupled to a heating element; receiving the control signal at each of the plurality of power interfaces; and modulating the power applied to a respective coupled heating element by a respective power interface in response to the control signal.
 12. The method of claim 11, further comprising receiving instructions at the power controller from a program operating on a terminal to change a power modulation to a heating element of the plurality of heating elements and changing the control signal at the power controller in response to the received instruction.
 13. The method of claim 11, further comprising receiving the control signal from the power controller at a carrier controller embedded in the substrate carrier, wherein the control signal is a serial packetized control signal and generating a unique control signal to each heating interface from the carrier controller.
 14. The method of claim 13 wherein the control signal from the power controller is an optical signal.
 15. The method of claim 11, further comprising measuring a voltage of the common power supply; measuring a current of the common power supply; generating a control signal to change a power state of a selected one of the heating elements; measuring a current of the common power supply after changing the power state; determining a difference of the first and second current measurement; and determining a temperature of the selected one of the heating elements using the determined current measurement difference.
 16. A plasma processing chamber comprising: a plasma chamber; a plasma source to generate a plasma containing gas ions in the plasma chamber; a power supply to supply power; a power controller to provide a control signal to control heating; and a substrate carrier to carry a substrate in the chamber for processing, the carrier having a plurality of resistive heating elements to heat the substrate by heating the carrier and a plurality of power interfaces each coupled to a heating element to receive the power from the power supply and the control signal from the controller and to modulate the power applied to a respective coupled heating element in response to the control signal.
 17. The chamber of claim 16, further comprising a terminal coupled to the power controller to control the operation of the power interfaces.
 18. The chamber of claim 16, wherein the carrier further comprises a fan-out distributor to receive the power from the power supply and distribute the received power to each power interface.
 19. The chamber of claim 16, wherein each power interface receives a pulse width modulated signal based on the control signal, the pulse width modulated signal having a duty cycle to modulate the power applied to respective coupled heating element. 